The present invention relates to drive belts whose cross-section has a substantially trapezoidal outer contour and which are formed essentially of at least one core closed on itself and of an assembly of riders mounted alongside each other on the core.
Such belts are used, for instance, in certain speed regulators which act by the spreading apart of conical-flange pulleys. In these regulators the drive torque is transmitted by compression of the riders against each other between the flanges of the pulleys and along the flattened annular core. Longitudinal sliding takes place between the core and the riders. In order to permit this movement, clearance is provided between the two side faces and the outer face of the core, on the one hand, and the riders, on the other hand. The inner face of the core remains frequently in contact with the riders, particularly in the regions where the belt is engaged between the flanges of the pulleys. These clearances permit a transverse backward and forward movement of the core with respect to the riders. These relative movements result in rubbing, heating and wear of the inner face and of the two side faces of the core.
The technique of the manufacture of the core (which is a flat belt) makes it possible to minimize the wear of the inner face of the core. However, the protection of the side faces requires individual treatment of each core, for instance, by covering the core with a protective fabric which adheres to the core.
The object of the invention is to eliminate the individual protection of the side faces of the core at the time of the manufacture thereof, while avoiding the relative backward and forward movement of the core within the riders, this movement being the major cause of the wear of the side faces of the core.
Thus, the invention consists in providing at least on one of the inner or outer faces of the core at least one longitudinal rib which is permanently housed within a corresponding portion of a cutout in each rider. This rib is preferably continuous.
The invention is advantageously combined with one of the following arrangements. They, on the one hand, further decrease the destructive friction and therefore the heating of the parts which move relative to each other and, on the other hand, reduce the noise, and furthermore, in the case of the last two, make it possible also to separate the transverse guidance function from the drive function of the movement of the riders.
In a second variant, the core is essentially formed of a reinforced or non-reinforced rubber or plastic material; the riders are essentially formed of metal; the rib of the core, at least in the portion thereof in contact with the corresponding portion of the cutout in each rider, is formed of a rubber or plastic material of high resistance to compression and wear; and the outer faces of the riders, at least in the portions thereof in contact with the pulley flanges, are formed of a rubber or plastic material of high resistance to compression and wear in contact with the metal of the pulley flanges.
In a third variant, the core is essentially formed of a reinforced or non-reinforced rubber or plastic material; each rider is formed of two longitudinally consecutive elements which are locked with respect to each other in the transverse direction of the belt; the first element is spaced from the core, has its outer faces in contact with the pulley flanges and, at least at its outer faces, is formed of a rubber or plastic material of high resistance to compression and wear in contact with the metal of the pulley flanges; the second element is spaced from the pulley flanges, comprises the cutout which houses the rib of the core and, at least along the cutout, is formed of metal; and the rib of the core, at least in the portion thereof in contact with the second element of the riders, is formed of a rubber or plastic material of high resistance to compression and wear in contact with the metal of the second element.
Finally, in a fourth variant, the first element of the riders is formed of a rubber or plastic material of high resistance to compression and wear in contact with the metal of the pulley flanges; the second element is formed of metal; and the rib of the core is formed of a rubber or plastic of high resistance to compression and wear in contact with the metal of the second element.
These riders are preferably arranged one behind the other on the core so that the first elements alternate with the second elements.